Servomotor with lubricated rotatable piston rod



y 1952 v F. E KLOSTERMAN 2,598,271

SERVOMOTOR WITH LUBRICATED ROTATABLE PISTON ROD Filed Jan. 8, 1947 2 SHEETS-SHEET l Ill /NVENTOR franc/3 f. Klosferman INDQWA W ATTORNEY May 27, 1952 F. E. KLOSTERMAN SERVOMOTOR WITH LUBRICATED ROTATABLE PISTON ROD Filed Jan. 8. 1947 2 SHEETSSHEET 2 34 f; x 32 Z 1 ;f; jg

. lNl/ENTOR gym/5 f. K/os/erman A TTORNEY Patented May 27, 1952 SERVOMOTOR WITH LUBRICATED ROTATABLE PISTON ROD Francis E. Klosterman, Louisville, Ky. Application January 8, 1947, Serial No. 720,707

9 Claims.

This invention relates to improvements in servo-motors of the non-rotating cylinder type which are particularly suited for use in operating chucks, clutches, punch presses and the like.

Heretofore, double acting air operated servomotors have been made in non-rotating cylinder types which are suited for some uses and in rotating cylinder types which are suited for other uses. In the rotating type, the cylinder rotates with the chuck spindle at speeds normally ranging from 100 to 400 R. P. M. Due primarily to cylinder rotation, the rotating type has a number of objections or drawbacks among which are: it requires considerable manufacturing care to produce an evenly balanced structure; it involves special connections for flowing air into and out of the rotating cylinder; it usually results in a somewhat cumbersome installation; and its operation involves the hazards necessarily incident to the rapid rotation of a part which usually is located near the operator and often is of substantial size.

The principal object of the present invention is to overcome these objections and drawbacks through the provision of a non-rotating type of cylinder which may be employed in most if not all installations where a rotating type has heretofore been required.

Another object is to provide a simple and compact form of servo-motor which is relatively inexpensive to manufacture and easy to install and operate.

Another object is to provide, in a double acting servo-motor, having a reciprocating and rotatable or non-rotatable piston rod, a novel form of piston rod seal which eliminates the stufiing box.

The invention is illustrated in the accompanying drawings wherein:

Fig. 1 is a vertical section through a double acting air cylinder constructed in accordance with my invention;

Fig. 2 is a modified form of piston head which may be substituted for one of the piston heads shown in Fig. 1; and

Fig. 3 is a vertical section through an air compressor incorporating the present invention.

The servo-motor shown in Fig. 1 comprises: a stationary open ended cylinder member designated by the numeral I; an end wall 2 closing one end of the cylinder member and containing an air flow connection 3; an end wall 4 closing Q18 opposite end of the cylinder and containing an air flow connection 5; and a series of tie bolts 6, only one of which is shown, connecting the end walls 2 and 4 and rigidly clamping them against the adjacent ends of the cylinder l. The end wall 4 is integrally formed with a sleeve I extending centrally into the interior of the cylinder l. The piston 8 is bored at 9 and counterbored at ID to receive the sleeve 1, and is adapted to reciprocate thereon, a working clearance being provided between sleeve 1 and bore Hl. One end of the piston carries an annular gasket ll held thereon by an annular plate and screws, the gasket serving to seal the joint between the cylinder and piston at one end, and the running clearance between the sleeve 1 and bore Ill. The opposite end of the piston has a chamber l2, and a gasket 14 and cover plate l3 serve to seal the chamber from the cylinder and seal the joint between the cylinder and piston at that end.

Chamber l2 contains a combined radial and end thrust bearing ii in which is journalled a hub l6 suitably secured, as by a threaded connection, to a hollow piston rod I! which passes through bore 9 in the piston and bore l8 in the sleeve 1. A duct 19 in the hub l6 connects with the bore 20 in the piston rod. A suitable lubricating nipple 2| is provided at the end of the rod, and lubricant under pressure can be introduced to bearing l5 through duct l9, bore 20 and nipple 2|.

The stationary end wall 4 is arranged toprovide a rotatable mounting for the adjacent end of a rotatable spindle 22 which carries the chuck or other device to be operated by the servo-motor. Accordingly, this end wall 4 is recessed toaccommodate a combined radial and end thrust bearing assembly 23 for the spindle 22 which carries the reacting thrust of the spindle against the cylinder head 4. The annular opening between the spindle and the outlying portion of the end wall 4 is closed by a cover plate 24, in order to retain lubricant in the bearing assembly 23.

The operation of the apparatus now will be described. The cylinder I is suitably carried on the machine in non-rotatable relation thereto, and is located at the end of rotating spindle 22. When air pressure is applied to the right end of the piston through connection 5, the piston exerts a thrust to the left which is transmitted by piston rod IT, by means of a collar or other suitable connection, to the chuck or other device operated thereby and carried by the rotating spindle 22. The piston rod I! thus is set into rotation, and the rotational end thrust between the piston and rod is carried by hearing IS. The piston is retained against rotation in the cylinder by the engagement of the packings l I and I4, which serve to seal the connection between the piston and cylinder toprevent air leakage. The reacting end thrust of spindle 22, on the cylinder, which is exerted to the left, is carried by bearing 23. The bearing 15 can be pressure lubricated through bores l9 and 2!! by means of the pressure lubricating fitting 2|. The introduction of lubricant under pressure at the fitting 2i forces air and excess lubricant in chamber 12 through the clearance space between the piston rod and bore 9, and between the piston rod and bore ill in bearing 1 into bearing 23. The bearing cover 24 prevents oozin of lubricant but allows escape of excess lubricant when lubricant under pressure is introduced at fitting 2 i.

The arrangement shown in Fig. 1 is intended to do Work or transmit power in one direction only, namely, toward the left as shown in Fig. 1. To transmit power in both directions, it is desirable to provide a double acting thrust bearing of Fig. 2 in place of a single acting thrust hearing shown in Fig. 1. The double acting thrust bearing shown in Fig. 2 comprises a closure plate 13a, a piston rod connection member tEa and another thrust bearing roller assembly lid.

As indicated previously, the present invention may be usefully incorporated in air cylinders of various types such as air compressor cylinders. An embodiment of this character is shown in Fig. 3. The compressor cylinder shown in Fig. 3

comprises: a cylinder member 25; end walls 28 O and 21, suction valve openings 28 and 29 and discharge valve openings 38 and 3!. The end wall 255 is integrally formed with a centrally located tubular bearing 32 projecting inwardly Within the cylinder 25 to provide an outer elongate seat for slidably receiving and encircling a snugly fitting piston and an inner elongate bore for slidably receiving a snugly fitting piston rod.

The piston 33 is a double acting piston which contains an inner elongate bore for slidably receiving the snugly fitting tubular bearing 32. This piston fits snugly within the cylindrical chamber 25 but, since the air pressure may be relatively high, the space between the cylinder member 25 and the outer periphery of the piston 33 is slidably sealed by piston rings 34 preferably mounted in the periphery of the piston 33. Likewise the space between the piston 33 and the outer periphery of the tubular bearing 32 is slidably sealed by piston rings 35 preferably mounted in the bearing 32 although they may of course be mounted in the bore of piston 33.

The piston rod 36 extends through the bore of tubular bearing 32 and is rigidly connected to the piston 33 adjacent that end of piston 33 which is adjacent to the end wall 21.

The compressor shown in Fig. 3 is provided with a conventional unloader 3T. Since the unloader 3'! is conventional, it is not deemed necessary to describe its construction or operation.

With this arrangement, the sealing rings 3-2 and 35 provide efiective seals between opposed chambers of the compressor and between chamber surrounding the bearing member 32 and the bore of that bearing member. This latter sealing is sufficiently effective as to eliminate the necessity of a stufling box. Of course, it will be understood that a stufling box may be employed and may even be desirable in some instances to reduce leakage as wear of the machine proceeds.

Having described my invention, I claim:

1. A servo-motor of the class described comprising: a stationary cylinder having front and rear end walls closing opposite ends of the cylinder; a tubular bearing centrally located on and rigidly secured to the rear end wall to project inwardly into the cylinder, said bearing providing an outer elongate periphery and an inner elongate bore extending through the bearing member and the rear end wall; a piston providing a relatively enclosed recess in the front end thereof and slidably mounted in the cylinder for movement longitudinally along the outer periphery of the bearing member, said piston being provided with an inner elongate bore to accommodate the tubular bearing; a hollow piston rod rotatably connected by a bearing assembly in said recess to the piston for rotational movement relatively thereto and for longitudinal movement therewith, said rod extending from said connection through the bore of the tubular member and projecting outwardly from the rear end wall, the connected end of the piston rod being in open communication with said recess, and arranged with the projecting end thereof to receive lubricant for said bearing assembly.

2. A servo-motor of the class described comprising: a stationary cylinder having front and rear end walls closing opposite ends of the cylinder; a tubular bearing centrally located on and rigidly secured to the rear end wall to project inwardly into the cylinder, said bearing providing an outer elongate periphery and an inner elongate bore extending through the bearing member and the rear end wall; a piston providing a relatively enclosed recess in the front end thereof and slidably mounted in the cylinder for movement longitudinally along the outer periphery of the bearing member, said piston being provided with an inner elongate bore to accommodate the tubular bearing; a hollow piston rod rotatably connected to the piston in said recess for rotational movement relatively thereto and for longitudinal movement therewith by a connector member rigidly secured to the piston rod and a bearing assembly between the connector member and the piston, said connector member having a lubricating bore therein; said rod extending from said connection through the bore of the tubular member and projecting outwardly from the rear end wall, the connected end of the piston rod being in communication with the lubricating bore of the connector member, and arranged with the projecting end thereof to receive a lubricant for lubricating the interior of said recess.

3. A servo-motor of the class described comprising: a cylinder having end closing walls; one end wall having a sleeve projecting into the cylinder providing a bore extending through the sleeve and end wall; a piston in said cylinder having a here at one end to receive said sleeve and reciprocable thereon; a piston rod extending through the bore in the sleeve and end wall and connected in rotatable relation to the piston adjacent the end of the piston bore, said rod providing a lubricant passage therethrough to the rotatable connection with the piston; and a pressure lubricating fitting on said rod connected to said passage.

4. A servo-motor as specified in claim 3 wherein the rotatable connection of the piston rod and piston is provided by a combined radial and end thrust anti-friction bearing.

5. A servo-motor as specified in claim 4 wherein said bearing is double acting.

6. An air cylinder of the class described comprising: a cylinder having heads closing the ends thereof; a piston in said cylinder providing a closed end and having an axial bore in the other end; a tubular sleeve on one head received in said bore; a piston rod extending through said sleeve with a working clearance; mean securing one end of said piston rod within the piston for relative rotatable and conjoint reciprocating movement; and means sealing the sleeve and bore against escape of air from the cylinder and permitting reciprocation of the piston on said sleeve.

7. An air cylinder of the class described comprising: a cylinder having head closing the ends thereof; a piston in said cylinder having an axial bore in one end; a tubular sleeve on one head received in said bore; an anti-friction bearing in said piston adjacent the end of said bore; a piston rod extending through said sleeve with a working clearance and secured to said bearing; and means sealing the sleeve and piston bore against escape of air from the cylinder and permitting reciprocation of the piston on said sleeve; and a pressure tight cover on the piston for said anti-friction bearing.

8. An air motor of the class described comprising: a. cylinder having end walls; a piston reciprocable in said cylinders and having an axial bore therein; a hollow sleeve extending from one end wall into said bore and providing a sliding bearing for said piston; means sealing the joint between said sleeve and piston bore; a combined end and radial thrust bearing in said piston; and a piston rod secured to said bearing and extending through said sleeve with a working clearance to the exterior of said cylinder.

9. An air motor of the class described comprising: a cylinder having end walls; a piston reciprocablein said cylinder and having an axial bore therein; a hollow sleeve extending from one end wall into said bore and providing a sliding bearing for said piston; said latter end Wall carrying an anti-friction thrust bearing on its exterior adapted to receive a rotatable spindle; means sealing the joint between said sleeve and piston bore; a combined end and radial thrust bearing in said piston; a piston rod secured to said latter bearing and extending through said sleeve with a Working clearance to the exterior of said cylinder.

FRANCIS- E. KLOSTERMAN.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,074,239 Miller Sept. 30, 1913 1,296,735 Arbuckle Mar. 11, 1919 1,513,090 Fornaca Jan. 4, 1927 1,804,002 Fantz May 5, 1931 2,272,620 Hoffar Feb. 10, 1942 2,296,145 Christensen Sept. 15, 1942 2,376,576 Cross May 22, 1945 2,393,410 Pine Jan. 22, 1946 FOREIGN PATENTS Number Country Date 226,589 Great Britain Dec. 18, 1924 574,901 Germany Apr. 21, 1933 

